Calling Java from C++ thru JNI

Question

Hi,
Can anybody help me on this...
I am trying to invoke a simple java method from c++.
I am using the reference example as in tutorial at
http://www-105.ibm.com/developerworks/education.nsf/java-onlinecourse-bytitle/52FFDF7067EAA64986256B87006A5D37?OpenDocument
My C++ program compiles without any errors, but when i try to create an EXE, I get the foll. error::
error LNK2001: unresolved external symbol __imp__JNI_CreateJavaVM@12
I am using JDK1.3, and also making use of jvm.dll, jvm.lib and jni.h files shipped with the JDK installer. Can anybody give me a clue on what is the error referring to?
Thx in advance

Answer 1

Hi, I have the same problem as you.. I have been tying to proof the example:
#include <stdio.h>
#include <jni.h>
void goTest(JNIEnv *pEnv);
main(void) {
     JavaVMInitArgs vm_args;
     JavaVMOption options[6];
jint res;
JavaVM *vm;
JNIEnv *pEnv;
     options[0].optionString = "-Djava.compiler=NONE"; /* disable JIT */
     options[1].optionString = "-Djava.class.path=c:\\_jni\\whiskey\\std"; /* user classes */
     //options[2].optionString = "-Djava.library.path=c:\mylibs"; /* set native library path */
     options[2].optionString = "-Xbootclasspath/a:c:\\_jdks\\ibm_1.3_0502\\lib\\tools.jar";
     options[3].optionString = "-Xdebug"; /* print JNI-related messages */
options[4].optionString = "-Xnoagent";
options[5].optionString = "-Xrunjdwp:transport=dt_socket,server=y,suspend=n";
     vm_args.version = JNI_VERSION_1_2;
     vm_args.options = options;
     vm_args.nOptions = 6;
     vm_args.ignoreUnrecognized = JNI_FALSE;
     /* Note that in JDK 1.2, there is no longer any need to call
     * JNI_GetDefaultJavaVMInitArgs.
res = JNI_CreateJavaVM(&vm, (void **)&pEnv, &vm_args);
if (res < 0) {
printf("failure in create java vm\n");
int loop=0;
while (loop==0) {
printf("waiting...");
goTest(pEnv);
void goTest(JNIEnv *pEnv) {
jclass javaClass;
jmethodID mid;
jint result;
javaClass = (*pEnv)->FindClass(pEnv,"JNITest");
mid = (*pEnv)->GetStaticMethodID(pEnv,javaClass,"java_tripleNumber","(I)I");
result = (*pEnv)->CallStaticIntMethod(pEnv,javaClass,mid,42) ;
I have do the following:
dlltool -k dllname jvm.dll def jvm.def --output-lib d:\jbuilder5\jdk1.3\jre\bin\classic\libjvm.a
gcc -Id:\jbuilder5\jdk1.3\include -Id:\jbuilder5\jdk1.3\include\win32 -g -c invoke.c
gcc -o invoke.exe invoke.o -Ld:\jbuilder5\jdk1.3\jre\bin\classic -ljvm
The executable file is created without problems, but when I run it..
Can't load "jdwp.dll", because Can't find dependent libraries
failure in create java vm
I have debbug it: gdb invoke
(gdb) b main
Breakpoint 1 at 0x4013aa: file invoke.c, line 85.
(gdb) r
Starting program: D:\MinGW\bin/invoke.exe
Breakpoint 1, main () at invoke.c:85
85 options[0].optionString = "-Djava.compiler=NONE"; /* d
isable JIT */
(gdb) n
86 options[1].optionString = "-Djava.class.path=c:\\_jni\\whiskey\\
std"; /* user classes */
(gdb) n
88 options[2].optionString = "-Xbootclasspath/a:c:\\_jdks\\ibm_1.3_
0502\\lib\\tools.jar";
(gdb) n
89 options[3].optionString = "-Xdebug"; /* print
JNI-related messages */
(gdb) n
90 options[4].optionString = "-Xnoagent";
(gdb) n
91 options[5].optionString = "-Xrunjdwp:transport=dt_socket,server=y,su
spend=n";
(gdb) n
93 vm_args.version = JNI_VERSION_1_2;
(gdb) n
94 vm_args.options = options;
(gdb) n
95 vm_args.nOptions = 6;
(gdb) n
96 vm_args.ignoreUnrecognized = JNI_FALSE;
(gdb) n
101 res = JNI_CreateJavaVM(&vm, (void **)&pEnv, &vm_args);
(gdb) n
0x503e41b1 in d_jbuilder5_jdk1_3_jre_bin_classic_libjvm_a_iname ()
(gdb) n
Single stepping until exit from function d_jbuilder5_jdk1_3_jre_bin_classic_li
bjvm_a_iname,
which has no line number information.
0x77e8860c in d_jbuilder5_jdk1_3_jre_bin_classic_libjvm_a_iname ()
(gdb) n
Single stepping until exit from function d_jbuilder5_jdk1_3_jre_bin_classic_li
bjvm_a_iname,
which has no line number information.
Program received signal SIGSEGV, Segmentation fault.
0x0040145a in goTest (pEnv=0x0) at invoke.c:124
124 javaClass = (*pEnv)->FindClass(pEnv,"JNITest");
(gdb)
.... How can I solve this problem..